> For the complete documentation index, see [llms.txt](https://boxlang.ortusbooks.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://boxlang.ortusbooks.com/boxlang-language/reference/built-in-functions/decision/isjson.md).

# IsJSON

Evaluates whether a string is in valid JSON (JavaScript Object Notation) data interchange format.

## Method Signature

```
IsJSON(var=[any])
```

### Arguments

| Argument | Type  | Required | Description                | Default |
| -------- | ----- | -------- | -------------------------- | ------- |
| `var`    | `any` | `true`   | The value to test for JSON |         |

## Examples

### isJSON Example

Returns true when the argument is a valid JSON value.

[Run Example](https://try.boxlang.io/?code=eJzLLPYK9vfTUFCKNtQx0jGOVVLQtOYCAD3kBNc%3D)

```java
isJSON( "[1,2,3]" );

```

Result: true

### Additional Examples

[Run Example](https://try.boxlang.io/?code=eJydj7FqwzAQhmf7KQ5NDmionBYKxUOTThlSirsFD6f0aASy3ZytGvfpKzkppK49NCAh8Yvv%2B08dm5aeXPmRgEVNNhOPzNgLCZ%2FImWk2TV0lIHZKpnJZCFjA4iHu%2FkC5qd4tQeVKTexR62ikULNoyx6eZETjGqPS5e3dfPEFDZ1pD9AQG7Tmizb583YkDFH%2B8372D%2Bpp%2BaquLWF1pb1lD82610zoI79fTfl%2F%2BW88gfRG3UtQl%2BvUHdqP3EMGR0fcb6nz%2F0ZEqbX2FcJ37A%2FIQ1m4%2BGwXR35FAoUMhxZxVMhztj9lbyGLi%2BmvvYSi0fhhhGGWb41ZwUw%3D)

```java
writeDump( label="Array", var=isJson( "[1,2,3]" ) );
writeDump( label="Single number value", var=isJson( 1 ) );
writeDump( label="String value", var=isJson( "susi12345" ) );
writeDump( label="String value with serializeJSON", var=isJson( JSONSerialize( "susi" ) ) );
writeDump( label="Boolean value with serializeJSON", var=isJson( JSONSerialize( true ) ) );
writeDump( label="CreateDateTime with serializeJSON", var=isJson( JSONSerialize( CreateDateTime( 2018, 1, 1, 1, 1, 1 ) ) ) );
qry = queryNew( "aaa,bbb", "varchar, varchar", [
	[
		"a",
		"b"
	],
	[
		"c",
		"d"
	]
] );
writeDump( label="Query", var=isJson( qry ) );

```

## Related

* [ArrayIsEmpty](/boxlang-language/reference/built-in-functions/decision/arrayisempty.md)
* [arrayIsEmpty](https://github.com/ortus-boxlang/boxlang-docs/blob/v1.x/boxlang-language/reference/built-in-functions/decision/arrayIsEmpty.md)
* [Attempt](/boxlang-language/reference/built-in-functions/decision/attempt.md)
* [IsArray](/boxlang-language/reference/built-in-functions/decision/isarray.md)
* [IsBinary](/boxlang-language/reference/built-in-functions/decision/isbinary.md)
* [IsBoolean](/boxlang-language/reference/built-in-functions/decision/isboolean.md)
* [IsClosure](/boxlang-language/reference/built-in-functions/decision/isclosure.md)
* [IsCustomFunction](/boxlang-language/reference/built-in-functions/decision/iscustomfunction.md)
* [IsDate](/boxlang-language/reference/built-in-functions/decision/isdate.md)
* [IsDateObject](/boxlang-language/reference/built-in-functions/decision/isdateobject.md)
* [IsDebugMode](/boxlang-language/reference/built-in-functions/decision/isdebugmode.md)
* [IsDefined](/boxlang-language/reference/built-in-functions/decision/isdefined.md)
* [IsEmpty](/boxlang-language/reference/built-in-functions/decision/isempty.md)
* [IsFileObject](/boxlang-language/reference/built-in-functions/decision/isfileobject.md)
* [IsIPv6](/boxlang-language/reference/built-in-functions/decision/isipv6.md)
* [IsLeapYear](/boxlang-language/reference/built-in-functions/decision/isleapyear.md)
* [IsLocalHost](/boxlang-language/reference/built-in-functions/decision/islocalhost.md)
* [IsNull](/boxlang-language/reference/built-in-functions/decision/isnull.md)
* [IsNumeric](/boxlang-language/reference/built-in-functions/decision/isnumeric.md)
* [IsNumericDate](/boxlang-language/reference/built-in-functions/decision/isnumericdate.md)
* [IsObject](/boxlang-language/reference/built-in-functions/decision/isobject.md)
* [IsQuery](/boxlang-language/reference/built-in-functions/decision/isquery.md)
* [IsSimpleValue](/boxlang-language/reference/built-in-functions/decision/issimplevalue.md)
* [IsStruct](/boxlang-language/reference/built-in-functions/decision/isstruct.md)
* [IsValid](/boxlang-language/reference/built-in-functions/decision/isvalid.md)
* [IsXML](/boxlang-language/reference/built-in-functions/decision/isxml.md)
* [IsXmlAttribute](/boxlang-language/reference/built-in-functions/decision/isxmlattribute.md)
* [IsXMLDoc](/boxlang-language/reference/built-in-functions/decision/isxmldoc.md)
* [IsXMLElem](/boxlang-language/reference/built-in-functions/decision/isxmlelem.md)
* [IsXMLNode](/boxlang-language/reference/built-in-functions/decision/isxmlnode.md)
* [IsXMLRoot](/boxlang-language/reference/built-in-functions/decision/isxmlroot.md)
* [LSIsNumeric](/boxlang-language/reference/built-in-functions/decision/lsisnumeric.md)
* [structIsEmpty](/boxlang-language/reference/built-in-functions/decision/structisempty.md)


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://boxlang.ortusbooks.com/boxlang-language/reference/built-in-functions/decision/isjson.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.